Another solution might be the ultra compact fission reactors being developed by nasa for powering a manned mission to mars. If you can generate 6 megawatts of power for the vasimr rockets you can travel to mars in less then 45 days. Some of the conce...
One engineering issue with a real life gundam would be the power source batteries will not make the cut the closest practical power source I can think of would be either a gas turbine or large diesel engine or a non conventional option a mono propell...